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View Full Version : Where the combustion air come from?


Ben Im
03-23-2013, 12:51 AM
the laundry room I inspect is 7x7x8 size, has a window but usually closed and door without any vent opening.
There are one 38000 BTU water heater & gas dryer & washer in this room
Is there any formula about room size vs BTU ?
John Arnold
03-23-2013, 03:46 AM
If you have less than 50 cubic feet of space per 1,000 BTU combined input, then you need additional combustion and makeup air.
wayne soper
03-23-2013, 03:46 AM
water heater unless it is electric, should not be in the laundry room. The dryer can pull the flame out of the chamber
Jim Robinson
03-23-2013, 06:36 AM
the laundry room I inspect is 7x7x8 size, has a window but usually closed and door without any vent opening.
There are one 38000 BTU water heater & gas dryer & washer in this room
Is there any formula about room size vs BTU ?

If this is a serious question, you aren't ready to be getting paid to do inspections for people. If this was a test or sample inspection, no problem. The combustion air requirements are pretty straight forwards and pretty basic stuff, and you should know that stuff before going out there and starting up an inspection business.
Charles Wilson
03-23-2013, 12:32 PM
The answer to your question is yes there is a formula. I would also suggest, assuming you do not already have it, a copy of Code Check Complete. Keep it with you when you do the inspections and get ready to write the reports. As someone told me years ago, the secret is not memorizing formulas and figures, the key is knowing where to find them and how to use them correctly.
Ben Im
03-23-2013, 01:52 PM
you 're right,,, but I knew the formula is exist. I only don't remember the numbers.
Anyway, I think the gas dryer is not included to BTU calculations, so I don't concern the dryer's BTU
Am I wrong?
water heater can not be in laundry room? even if there is enough combustion air supply?
Mike Lamb
03-23-2013, 05:22 PM
water heater unless it is electric, should not be in the laundry room.

Wayne, do you have a reference for this statement? Sounds like a myth.

It's true a gas dryer can adversely affect the venting operation of a non-direct vent gas water heater (or furnace) but I've never seen that they can't be in the same room.

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Anyway, I think the gas dryer is not included to BTU calculations, so I don't concern the dryer's BTU
Am I wrong?


Yes, you are wrong. You need to beef up on this stuff. It could save a person's life.